HRR: cardio and respiratory adaptations in pregnancy Flashcards
(37 cards)
What are the main factors for resistance in terms of blood flow?
Length of the vessel, blood viscosity, radius of the vessel
How do we calculate systemic vascular resistance?
SVR = [(MAP - RAP)/CO] x 80
How do we calculate pulmonary vascular resistance?
PVR = [(PA pressure - LAP)/CO] x 80
How does our body help manage flow resistance?
Our flow systems are arranged in parallel; this helps us direct flow to various places or shut down flow where we don’t need it
Describe blood flow to the uterus throughout pregnancy.
At the start of pregnancy, the uterus receives around 2-4% of CO. By the end, about 15-20% of CO goes to the uterus.
What happens to blood volume in pregnancy?
It increases dramatically
Does plasma volume or red cell volume increase faster during pregnancy? What are the implications of this?
Plasma volume; this leads to physiologic anemia that lowers resistance to flow by lowering blood viscosity and protects against symptomatic blood loss during childbirth.
Pregnancy is ___ in terms of thrombosis.
Prothrombotic; an attempt to decrease blood loss
Compare CO in left lateral decubitus position and supine during pregnancy.
Higher in left lateral decubitus! We can place pregnant patients on their left side to help boost maternal CO.
What is CO?
CO = SV x HR
What is stroke volume?
Volume of blood from ventricles per beat
Give the three equations for CO.
- CO = MAP/SVR
- CO = SV x HR
- CO = VO2/(CaO2 – CvO2)
Describe SVR in pregnancy.
There is a huge drop up until about week 20. After that, it will creep back up, but not to pre-pregnancy levels.
Describe mean vascular resistance in pregnancy.
There is a very slight increase followed by a gradual increase back to around pre-pregnancy levels.
What happens to BP in pregnancy?
There will be an initial drop from the low SVR, but it reaches its normal levels as pregnancy goes on.
Which drops in pregnancy: SBP or DBP?
DBP! This is from the drop in SVR.
What happens to the pulse pressure in pregnancy?
It initially widens due to lower SVR lowering DBP. It will even out as the SVR starts to go back up.
Describe progesterone and vascular tone.
Progesterone reduces cytosolic calcium, desensitizes angiotensin II receptors, and promotes remodeling of blood vessels to increase vessel number all to decrease vascular tone and promote muscle relaxation.
What is Ang 1-7?
A vasodilatory peptide
What happens to Ang II in the 3rd trimester?
There is a huge increase! However, BP doesn’t really change.
What happens to Ang II and progesterone in preeclampsia?
Decreased Ang II and progesterone; it is thought that low progesterone means less desensitization of ang II receptors, meaning less Ang II is needed but higher BP may occur.
What happens to A-V O2 difference in pregnancy?
It initially falls up to week 20 but returns back to normal as pregnancy progresses. This can plug into the Fick equation to explain the increase in CO.
Describe arrhythmia in pregnancy.
Usually benign and often PAC and PVC’s or nonspecific ST-T changes.
What happens to pre-existing arrhythmia during pregnancy?
They often worsen.
